Grade 5 Science

Core Unit: Matter and its Changes

1. Describe the atom as a basic unit of matter.
2. Explain the relationship between atoms and elements.
3. Distinguish between atoms and molecules.
4. Describe how molecules form.
5. Explain the relationship between molecules and compounds.

1. Distinguish between physical properties and chemical properties of substances.
2. Identify some physical properties of objects.
3. Identify some chemical properties of objects.
4. Measure the mass and the weight of some objects.
5. Compare solutions with other mixtures.
6. Observe and describe some physical changes.
7. Observe and describe some chemical changes.

Take the tube marked DW and add a small piece of zinc to it. A piece half the size of a dime would be good. Have students make observations of the contents over the next ten minutes.

Let both test tubes sit until the next day. Have students note any changes which have occurred in either test tube. Get two small flat dishes (plastic Petri dishes, plastic container lids, saucers). Have students label one dish DW and pour in some of the DW solution, being sure to leave any solid behind.Label the other dish TW and repeat the above procedure for the TW solution. When the liquid has evaporated, have students examine and describe the residue on each dish.

This activity requires the students to organize and interpret the evidence from their observations. Each group or pair can present to the class what they have discovered, and similarities and differences of the reports can be discussed.

Working in pairs, the students can half fill a jar with a sample of the soil. To a jar of the same size, half-filled with distilled water, add the soil sample. Stir the mixture to make a slurry and then let it settle. Repeat the stirring once or twice. Let the mixture settle and pour off the liquid through a filter. Put some of the filtrate onto a shallow dish to evaporate and examine the residue once the liquid has evaporated.

Can the residue be identified? Why is it present in some soils but not in others? Interview some farmers about the effect of saline soils on plant growth.

Have each group list their items and then agree on an estimated mass, in grams, for each one. Record the prediction. Encourage the students to give all of the group members an opportunity to make predictions. Use a balance to measure the masses to the nearest 0.1 g. Compare the accuracy of each prediction. Was the object which was assigned the heaviest predicted mass also the object which had the heaviest measured mass?

Give each group an object which is heavier than any of those in their original samples. Ask them to predict its mass, and then record that prediction. After they have measured and recorded its mass, have them exchange this article with that from another group (have one three-way exchange if there are an uneven number of groups) and measure the mass of the exchanged object. Compare their value with the value measured by the other group. If there is a significant difference in the values obtained, ask them to determine some way to resolve the discrepancy.

As an alternative, each group could be given a different type of mixture to separate. Some combinations are salt and pepper, sand and salt, sand and staples, vermiculite and plastic beads, sand and iron filings, salt and iron filings, sand and sawdust.

Ask each group to describe the observations which indicate that a phase change is occurring. A list of phase changes which the group members identify from their experience can be compiled. Discuss the factors which influence the rate of the change. How is this related to the cool feeling when a swimmer emerges from the water into a wind?

If dry ice is used, make sure that the students do not touch it to bare skin. In larger centres, dry ice may be obtained from welding supply stores. In smaller centres, it may be used to refrigerate produce and haul frozen foods in to the grocery store. Inquire at the store. It may be stored a short time if wrapped in layers of newspaper and placed in a deep freeze.

Unless the classroom air is very dry, a mixture of equal volumes of ammonium nitrate fertilizer (48-0-0) and water stirred in a jar will become cold enough to cause frost to form on the outside of the jar. A jar with an ice-water mixture will cause water to condense on the outside.

Challenge them to try floating a paper clip, a small piece of aluminum foil, some dry grains of sand, and some wet grains of sand on the surface of water, cooking oil, and alcohol. Describe the shape of the surface of the water surrounding any object you can get to float on the water. If none of the objects above will float on the surface, use a small piece of a styrofoam meat tray, and describe the surface shape of the water near its edges.

Ask them to fill a jar level-full with water. Predict how many drops can be added before the jar overflows. Carefully add drops to the centre of the water surface. Periodically look from the side across the top of the jar to observe the height of the water. Try the same thing with alcohol and oil.

What happens if a mixture of alcohol and water is used? Each group might be responsible for investigating the properties of a different proportion: 90% alcohol/10% water; 75% alcohol/ 25% water: and so on. Each group could report to the group on its findings. What is the effect of adding 3 drops of liquid dishwashing detergent or Kodak Photoflo (tm) to 100 mL of water? Does it change the way water behaves?

If long, small diameter test tubes or cylinders are available, viscosity can be measured by the length of time it takes a plastic bead to fall through the liquid.

One way to obtain a sample is to twin your class with a class whose school district borders on the ocean. Offer to trade something for a sample of sea water. (A two litre bottle filled almost full, packed in a sturdy box surrounded by crumpled newspaper or reused styrofoam packing peanuts, should get through the mail unscathed.) You could offer them some Saskatchewan slough water, some fossils, some wheat, canola, barley or lentil samples, or ask them to request something.

Perhaps a family member of one of the students could bring some seawater back after a trip. Sea water should not be packed in checked luggage on an airplane, since the luggage compartment is not heated and temperatures in the low stratosphere may approach -50 °C.

Instead of using sea water, samples from alkali lakes such as the Quill Lakes or Old Wives Lake can be used. Samples can also be obtained from lakes which contain sodium salts, such as Little Manitou Lake near Watrous.

Ask the students to generate other problems to investigate. Questions such as the following may arise: Does diluting the solution with water affect the bubbles? Can objects be stuck through a bubble without breaking it?

If you wish to have multitudes of bubbles floating in the room, ask the students to investigate whether there is a relationship between the size of a bubble and the time it will float in still air. Can they catch a bubble with their hand, or on a pencil?

Create a class list of all the places corrosion of metals is noticed in the classroom, school, homes, and community. An extension might be to find out about various ways of preventing corrosion and try to test them with the nails and jars.

As an extension, students could suggest other variables such as temperature, amount of light, solvent type which might affect the outcome of the experiment. They could then design experiments to test these variables for effect. The concept of controlling all other variables which have been shown to cause an effect should be emphasized. This can be discussed with the students as the principle of fairness in experimenting. If testing to see whether copper or zinc corrodes more, it would not be fair to put one in salty water and leave the other in the air.