Task 1 · easy
Atoms in H2O
How many hydrogen and oxygen atoms does one H2O molecule contain? And give me the number of all the atoms.
Hint and solution →Original practice tasks · Chemistry · Class 7
Elements, molecules and chemical compounds — tasks with solutions
Start with the easier exercises and work your way up. Every task has a hint and a full step-by-step solution — try it on your own first, then unlock the solution and compare.
Easy
5
Medium
4
Hard
3
Task 2 · easy
Atoms in CO2
Count the atoms in one CO2 molecule.
Hint and solution →Task 3 · easy
O2 element or compound?
Does O2 represent a simple substance or a chemical? Explain.
Hint and solution →Task 4 · easy
Atoms in NH3
How many atoms of each element and how many atoms does NH3 contain together?
Hint and solution →Task 5 · easy
Atoms in CH4
Count the number of atoms in one CH4 molecule.
Hint and solution →Task 6 · medium
Save Simple Pattern
The record is to represent a molecule composed of 2 H and 1 O. What's the pattern?
Hint and solution →Task 7 · medium
Model C and O
Save the formula of a molecule containing 1 C and 2 O atoms.
Hint and solution →Task 8 · medium
H2 and H2O
Classify H2 and H2O as a straight substance or a chemical.
Hint and solution →Task 9 · medium
Composition of NaCl
How many different elements are present in the NaCl formula and in what numerical ratio are Na to Cl?
Hint and solution →Task 10 · hard
Three H2O molecules
How many H, O and all of these atoms contain three H2O molecules?
Hint and solution →Task 11 · hard
Two CO2 molecules
Count the atoms in 2 CO2 particles.
Hint and solution →Task 12 · hard
Comparison of two molecules
Compare one H2O molecule and one CO2. How many atoms does each have in total and how many different elements does it contain?
Hint and solution →Karta pracy do druku
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Otwórz kartę pracy →After the tasks
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